/*
THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
SOFTWARE CORPORATION ("PARALLAX").  PARALLAX, IN DISTRIBUTING THE CODE TO
END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
IN USING, DISPLAYING,  AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
FREE PURPOSES.  IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES.  THE END-USER UNDERSTANDS
AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.  
COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
*/
/*
 * $Source: f:/miner/source/pslib/rcs/lzw.c $
 * $Revision: 1.8 $
 * $Author: john $
 * $Date: 1994/02/01 13:23:51 $
 *
 * Based on lzw15v.c from Data Compression book.
 * CompressFile and Expandfile have been replaced by cfread and cfwrite.
 *
 * $Log: lzw.c $
 * Revision 1.8  1994/02/01  13:23:51  john
 * *** empty log message ***
 * 
 * Revision 1.7  1993/10/22  17:50:43  yuan
 * Fixed the hard to track down bug
 * 
 * Revision 1.6  1993/10/18  18:00:13  yuan
 * Fixed memory alloc errors.
 * 
 * Revision 1.5  1993/09/21  17:22:24  yuan
 * *** empty log message ***
 * 
 * Revision 1.4  1993/09/21  17:16:25  yuan
 * cleaning up
 * 
 * Revision 1.3  1993/09/14  13:11:57  yuan
 * cfread and cfwrite have been changed into lzw_expand and lzw_compress.
 * the new cfread and cfwrite functions are now in library.c
 * lzw_compress returns the compressed buffer and a parameter *size.
 * 
 * Revision 1.2  1993/09/09  17:45:56  yuan
 * tab added to ERROR messages
 * 
 * Revision 1.1  1993/09/08  16:15:03  yuan
 * Initial revision
 * 
 * Revision 1.3  1993/07/24  19:05:22  yuan
 * *** empty log message ***
 * 
 * Revision 1.2  1993/07/22  11:27:29  yuan
 * No change
 * 
 * Revision 1.1  1993/07/21  15:28:48  matt
 * Initial revision
 * 
 *
 */

#pragma off (unreferenced)
static char rcsid[] = "$Id: lzw.c 1.8 1994/02/01 13:23:51 john Exp $";
#pragma on (unreferenced)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "library.h"
#include "mem.h"

//#define DEBUG_ON 1
//#include "error.h"

#define BITS                       15
#define MAX_CODE                   ( ( 1 << BITS ) - 1 )
#define TABLE_SIZE                 35023L
#define END_OF_STREAM              256
#define BUMP_CODE                  257
#define FLUSH_CODE                 258
#define FIRST_CODE                 259
#define UNUSED                     -1

unsigned int find_child_node( int parent_code, int child_character );
unsigned int decode_string( unsigned int offset, unsigned int code );

char *CompressionName = "LZW 15 Bit Variable Rate Encoder";
char *Usage           = "in-file out-file";

typedef struct {
    int code_value;
    int parent_code;
    char character;
} DICTIONARY;

DICTIONARY * dict;

char * decode_stack;
unsigned int next_code;
int current_code_bits;
unsigned int next_bump_code;

void InitializeDictionary()
{
	unsigned int i;

	for ( i = 0 ; i < TABLE_SIZE ; i++ )
		dict[i].code_value = UNUSED;

	next_code = FIRST_CODE;
    current_code_bits = 9;
    next_bump_code = 511;
}

void InitializeStorage()
{
	//MALLOC( dict, DICTIONARY, TABLE_SIZE );//won't compile, hack below -KRB
	//MALLOC( decode_stack, char, TABLE_SIZE );
	dict = (DICTIONARY *)malloc(TABLE_SIZE*sizeof(DICTIONARY));
	decode_stack = (char *)malloc(TABLE_SIZE*sizeof(char));
}


void FreeStorage()
{
	free(dict);
	free(decode_stack);
}

ubyte *lzw_compress( ubyte *inputbuf, ubyte *outputbuf, int input_size, int *output_size ) {
    BIT_BUF *output;
    int character;
    int string_code;
    unsigned int index;
    int i;

    output = OpenOutputBitBuf();
    if ( outputbuf == NULL ) {
        //MALLOC( output->buf, ubyte, input_size); //Another compile hack -KRB
		output->buf = (ubyte *)malloc(input_size*sizeof(ubyte));
        if (output->buf == NULL) {
            printf("    ERROR : OpenOutputBitBuf - Not enough memory to read buffer.\n");
            exit(1);
        }
        outputbuf = output->buf;
    } else output->buf = outputbuf;

    InitializeStorage();
    InitializeDictionary();
    string_code = ( *inputbuf++ );
	for ( i=0 ; i<input_size ; i++ ) {

		if (output->current_byte+4 >= input_size) {
            CloseOutputBitBuf( output );
            FreeStorage();
            free( outputbuf );
            *output_size = -1;
            return NULL;
        }
        character = ( *inputbuf++ );
        index = find_child_node( string_code, character );
		if ( dict[ index ].code_value != - 1 )
			string_code = dict[ index ].code_value;
        else {
			dict[ index ].code_value = next_code++;
			dict[ index ].parent_code = string_code;
			dict[ index ].character = (char) character;
            OutputBits( output,
                        (unsigned long) string_code, current_code_bits );
            string_code = character;
            if ( next_code > MAX_CODE ) {
                OutputBits( output,
                            (unsigned long) FLUSH_CODE, current_code_bits );
                InitializeDictionary();
            } else if ( next_code > next_bump_code ) {
                OutputBits( output,
                            (unsigned long) BUMP_CODE, current_code_bits );
                current_code_bits++;
                next_bump_code <<= 1;
                next_bump_code |= 1;
            }
        }
    }
    OutputBits( output, (unsigned long) string_code, current_code_bits );
    OutputBits( output, (unsigned long) END_OF_STREAM, current_code_bits);
	*output_size = output->current_byte+1;
	//printf("Outputsize %d\n", *output_size);
    CloseOutputBitBuf( output );
	FreeStorage();

	//mem_validate_heap();


	return outputbuf;
}


ubyte *lzw_expand( ubyte *inputbuf, ubyte *outputbuf, int length ) {
    BIT_BUF *input;
    unsigned int new_code;
    unsigned int old_code;
    int character;
    unsigned int count;
    int counter;

	//printf("Input Size %d\n", length);


    input = OpenInputBitBuf( inputbuf );
	if ( outputbuf == NULL )
		//MALLOC(outputbuf, ubyte, length);//Another hack for compiling -KRB
		outputbuf = (ubyte *)malloc(length*sizeof(ubyte));
    InitializeStorage();
    counter = 0;
    for ( ; ; ) {

		//mem_validate_heap();

		InitializeDictionary();
        old_code = (unsigned int) InputBits( input, current_code_bits );
		if ( old_code == END_OF_STREAM ) {
            CloseInputBitBuf( input );
			return outputbuf;
        }
        character = old_code;

		if (counter<length) {
			outputbuf[counter++] = ( ubyte ) old_code;
		} else {
			printf( "ERROR:Tried to write %d\n", old_code );
			exit(1);
		}

        for ( ; ; ) {

			//mem_validate_heap();

			new_code = (unsigned int) InputBits( input, current_code_bits );
            if ( new_code == END_OF_STREAM ) {
				//printf("\nEND OF STREAM at %d bytes\n", counter);
                CloseInputBitBuf( input );
                FreeStorage();
				return outputbuf;
            }
            if ( new_code == FLUSH_CODE )
                break;
            if ( new_code == BUMP_CODE ) {
                current_code_bits++;
                continue;
            }
            if ( new_code >= next_code ) {
				decode_stack[ 0 ] = (char) character;
                count = decode_string( 1, old_code );
            }
			else    {
                count = decode_string( 0, new_code );
			}
            character = decode_stack[ count - 1 ];
			while ( count > 0 ) {
				// This lets the case counter==length pass through.
				// This is a hack.
				if (counter<length) {
					outputbuf[counter++] = ( ubyte ) decode_stack[ --count ];
				} else if (counter>length) {
					printf( "ERROR:Tried to write %d\n", decode_stack[ --count ] );
					exit(1);
				} else
					count--;
			}
			dict[ next_code ].parent_code = old_code;
			dict[ next_code ].character = (char) character;
            next_code++;
            old_code = new_code;
        }
    }
}


unsigned int find_child_node( int parent_code, int child_character ) {
    unsigned int index;
    int offset;

    index = ( child_character << ( BITS - 8 ) ) ^ parent_code;
    if ( index == 0 )
        offset = 1;
    else
        offset = TABLE_SIZE - index;
    for ( ; ; ) {
		if ( dict[ index ].code_value == UNUSED )
            return( (unsigned int) index );
		if ( dict[ index ].parent_code == parent_code &&
			 dict[ index ].character == (char) child_character )
            return( index );
        if ( (int) index >= offset )
            index -= offset;
        else
            index += TABLE_SIZE - offset;
    }
}


unsigned int decode_string( unsigned int count, unsigned int code ) {
    while ( code > 255 ) {
		decode_stack[ count++ ] = dict[ code ].character;
		code = dict[ code ].parent_code;
    }
    decode_stack[ count++ ] = (char) code;
    return( count );
}